The invention is a configuration of a deformable mirror that permits easy actuator replacement. What is unique is the use of shaped-memory alloys to achieve this in a minimum space. This characteristic makes the invention applicable to high spatial frequency deformable mirrors such as are currently used in atmospheric correcting system (SAAO) and airborne laser weapon programs where the actuators are 7 mm apart.
As discussed in U.S. Pat. No. 5,745,278, deformable mirrors primarily intended for use as a beam train optic require frequency response, reliability, and low cost of manufacture as critical to the design, performance and usefulness. Thus the invention has particular usefulness in deformable mirrors that are used in adaptive optical systems. This would include low and high energy beam train configuration; that is both atmospheric correcting systems (SAAO) as well as laser weapon systems.
A deformable mirror which is used as a downstream optic in conjunction with a substantially larger optical system which is disposed upstream thereof must possess a high degree of sensitivity with respect to its ability to make highly minute adjustments to the reflective surface of the mirror. This is because such optical downstream mirrors represent the upstream optics in miniature. Such mirrors have a diameter in the range of five to fifteen inches, but for the larger sizes use on the order of about one thousand separate piezoelectric actuators to effect such adjustments. As can be expected, the nearly one thousand piezoelectric actuators used are highly miniaturized and make assembly and disassembly of the approximately one thousand piezoelectric actuators and the deformable mirror, when necessary, painstakingly tedious.
Current state-of-the art deformable mirrors such as SAAO must be satisfied with degraded performance if any of its 941 actuators fail since they are very difficult to replace. This replacement includes a complete replacement of the optical faceplate, a very difficult process. It is known to mechanically decouple the nose of the actuator from the back of the face plate, such as by cutting it with a wire saw. Other techniques involve melting epoxy joints with the application of heat to remove actuators. Heretofore, however, there are no known methods that utilize shaped-memory alloys, either with cooling or heating for replacing individual actuators.
Thus an object of the invention is to permit easy replacement of actuators in deformable mirrors thus maintaining their required performance characteristics without degradation with reasonable cost and schedule impacts.
Accordingly, it is an object of the present invention to provide deformable mirror actuation using individual piezoelectric actuators connected via shaped-memory alloys to the reaction plate thereby permitting disassembly inherent in systems utilizing such actuators.
Still a further objective of the invention is to provide a stress and strain free connection between the mirror and the supporting structure.
Yet still a further object of the invention is to provide a method of disassembly and reassembly that does not require high or low temperatures (below -60.degree. F.).
Yet still a further object of the invention is to provide a means of in situ actuator replacement.